Present devices or jigs are formed by two frames that are hinged to each other by means of two intermediate levers that co-operate with the two frames to form a hinged parallelogram.
One of the frames possesses means for fastening it to the vehicle body in register with the door opening. The other frame possesses means for supporting the door itself. In certain applications, these support means include a third frame that is hinged to the second frame and that actually supports the door.
Such assembly jig structures are usually made by a machine welding technique with manufacturing tolerances that are large in order to keep cost price down. In particular, the pivots of the hinges between the frames are of the door hinge type with hinge pins that co-operate with eyelets in a hinge plate or strap. The accuracy with which such hinge portions are assembled by welding requires a considerable amount of slack to be arranged between the knuckle and the eye, which slack degrades the accuracy of the relative positioning of the frame and thus of the positioning of the door panel relative to the body. Unfortunately such positioning needs to be accurate, at least when the frames are pressed one against the other and the door is close to its opening. In addition, that large amount of slack leaves a gap that becomes filled with door treatment material (paint, stripper, . . . ), which can lead to the pivots rapidly becoming clogged such that provision must be made for frequent cleaning, thus requiring considerable action to be taken on the equipment.
In order to remedy those drawbacks, proposals have been made—see FR 2 854 862—for a vehicle door mounting jig that comprises a first frame with means for adjustably fastening it on a vehicle body close to a door opening, and a second frame with means for supporting the vehicle door on said second frame, connection arms for connecting the first frame to the second being hinged to the first frame and to the second frame so as to co-operate therewith to form a deformable parallelogram in which the hinges between the arms and the frames are ball joints.
That disposition is entirely satisfactory in production. However while it is being constructed it requires considerable accuracy in the geometrical fastening of the ball joints in each jig, which fastening, in order to achieve such accuracy, constitutes considerable expense in terms of labor and increases the cost price of jigs.